Magnetic stand with adjustable shunt



Dec. 27, 1949 R. B. ROOF 2,492,238

MAGNETIC STAND WITH ADJUSTABLE SHUNT Filed Nov. 21, 1947 T511. 5 E m IN V EN TOR.

Karma/v0 6. #00;

patented Dec. 27, 1949 UNITE D: Sl-TAfl ES BATE? NT OFF ICE.

MfiGNETQIG-JST AN D WITH eADJUSTABLE SHUNZEJ ltavmond'Bjnoof, Battle Creek, Mich.

Applicationflnvemher 21, 1-945;- Seri'al No; 787,303

51-C ai'm5t. (Cl.l.175-.-3fi.-7

' hi v nt on, elates to, magnet c holdin mechanisms, and: more: particularly; to: improved structural features thereof. Y

Broadly the invention comprehendsg the; prosionlof hol i g;devi n hape manen ma ne ariety 1- w erein a. shu t ap? sanrovid d; n a mea fl lp th Oithe device!- g f Although numerous" permanentemagnetuhold ng devic s are; available, hen are either me parativelyf arge in size o o'notz no sess mple magnetic attractive force as to ,be efffii tiyely p1i b1 1 anyl e u rements of. ser, T prese t y; v sed, magnetic; ol er throu han efi qt ver ne m ntof nermane tvm p rpole piec nd. ma n t hunt. members. provid n a shunt p. her between as ade-nossi letlie provision f. compar iv-ely sm ler-.71 mane i old s ha r t f re avai ablah v e proton tionately greater v magnetic, attraction-Jones:- Thi mak s ossible he ap l cat n soft; tins, spninciple magnetic. nds hat l an be ti ized. int-nieces, previo ly naccessib e tot arge a ds,

ct of the nv ntion.visa hegpr visionct mel lm e et c old g eviceshavingiugnma neticattraction gualities,

Another object of the invention isflihg; p r yi- 01 of e nen m gnet c.hold ns devibeshavs, t e sedi a netie attraction -forceiaslcon pa e o r ous y. devised. e manent magnetic, holding devices g n t e v b e t (the, v ntionlisl he' DRI E o f a refi ement.,maenet dholdine device having a shunt gap in a flux paththereot provide ing great holdin str ngth in themaionflux path thereof,

A further object of, the invention is the; provi= i n a n ti ld ne dev ce applicable f n holdin dial indicators for use. with machine tools with a sufiicient" holding force i012 accurate dialindicating readings in connection withvthe tools operation.

A further objectoi the invention isthe provision of a permanent magnethol'ding device having a shunt'circuit in a magnet ic. flux path thereof and mechanism in theshunt circuit for controlling the magnetic flux in the'magneticfl flux holding circuit.

Other objects and' advantages oi the invention will appear from the following dQSClfipfiOI l taken in connection with: the drawings, forming a part of the specification; and in which:

Fig. 1 is a vertical side plan view of ja mag; netic stand, embodying the instant invention;

Fig. 2 is a vertical cross-sectional. view taken substantially along line 2=-2 'of Fig; 1

Riga. 3:; is ,a; vertical cross-sectional view. taken Substantially along line ,3.-5--3:Of Fig; 25;

Figs; 4, is, a. horizontal cross-sectional View aken 1vsubstantially' along.- line 4'-4:\. 0f niglzg...

Ri a-.45: is: a; perspective; View ofthe magnetic =1 device of; the magnetic. stand-i: Fig, ,1; gr; 6 is;v a vertical, crossesectionall view ofa modified form of magnetioholding;device;

: is; -a fragmentary, vertical cross-sectional view taken substantially-z along: line 1-1 2 of! Fig. fiend-2. c

Fig. 8 is a/fragmentaryg side planview of a modifiedjf OEIILO'f :the; shunt circuitlcontrol means heilvn-bvEigsfi-and '7.

Thevzpresentt invention tisdirectedsati the." provision; of: magnetic holdin devices: having; great strength holding or magnetic, attraction :q'ualities sq as; to; be primarily adaptableetoystandszfor supporting di-alzindicatorsq and the;like:.for use witmmaehine tools. Througlrthe: attainment of high magnetic holding force, it ,isspossiblatosmake magnetic holding devices of aisize for use: in placesgona machine tools and the likewvith, ample holding forceywhere larger holding :deviceawould be inaccessible;

This greater magnetic; holding strengthiseatetainedf through the arrangement of permanent magnet,.andpole-piecesin such a manner and. p rovidingean shunt circuit having a shunt gap; therein efiective to increase-tide magnet/1oz hold+= ing qualities ot the major flux; circuit :produced when thel holding deviceis; placed in, magnetic.- holdingzpositions Under conditions where'it is desired to effect an easmremoval .of :the magnetic holding-device from a holding. position a shunt circuit ;c0ntrol-. ling; mechanism.- is provided. which. can be 1 easily;- manipulated to-provide a. complete shunting ofh thev magnetic holdingsqualities 1 of the device wherein; only residual strength remains and the devicecan be readily removeclirom its holding position;v When; it isagai-n desired:ltovefiectaaa maximum strength holding operation, .-.of :thedevice, the, control mechanism. is l manipulated .to..

a position presenting an air gap-,or shunt ap? in, the, shunthcircuit and thereby restoring the...

maximmnmagnetic tholding quality of the. .maiQ T- magnetic flux circuit.

Referring to. the drawings for more-specificdetails of; theinvention, wherein likelnumerals refer.

"dicator l6 appropriately clamped to the stem 14;

3 This stand is adaptable to use in connection with machine tools and the like wherein the mechanism i2 is by magnetic attraction held to a portion of a machine tool and the indicator is moved as desired into engagement with work to be operated upon by the machine.

The mechanism [2 which constitutes the basis of this invention comprises a permanent magnet l8 suitably clamped between a pair of pole pieces or plates 26 and 22 respectively of high magnetic permeability qualities by a bolt 24 of non-magnetic material extending through the pole pieces 20 and 22 and magnet l8, and a pair of plates 26 and 28 respectively arranged in perpendicular relation to the magnet and pole pieces and arranged on ends 38 and 32 respectively of pole pieces 20 and 22.

The plates 26 and 28 of high magnetic permeability material are so arranged relative to the pole pieces and magnet as to extend toward one another and provide an air gap A therebetween,

more substantial thickness than plates 26 and 28 are provided having a passage 46 extending therebetween and having rotatable therein in close bearing relation a shaft 48 composed of a laminated structure of a strip of non-magnetic material 50 such as brass or the like sandwiched between a pair of substantially semi-circular crosssection members 52 of high permeability material such as mild steel or similar metal. The inwardly extending ends of the plates 42 and 44 are provided with semicircular concave portions 54 and 56 respectively within which the semi-circular exterior surfaces of the shaft are arranged to be in good physical contact. The shaft 48 is provided with a suitable manually actuable knob 58 for the proper setting of the shaft relative to the plates 42 and 44 for an on or off operation of said air gap defining a narrow rectangular passage or opening extending the length of the plates therebetween. The plates 26 and 28 are held in place upon the pole pieces by a block 34 of nonmagnetic material suitably secured to the pole pieces by screws 36 of non-magnetic material extending through the block and plates into the pole pieces 20 and 22.

The block 34 is provided with a threaded hole 38 therein for the receipt of the screw threaded end of support stem I4 for securely holding the stem relative to the mechanism [2.

The extremities of the pole pieces 20 and 22 oppositely disposed from the ends and 32 provide the principal holding or magnetic attraction ends of mechanism I2 and are arranged in parallel relation to block 34 and plates 26 and 28. The two vertical exposed sides of pole pieces 20 and 22 also serve as holding surfaces if it is not convenient to use the extremities of 20 and 22 in certain applications.

As a means of inhibiting magnetic particles fromclinging to the permanent magnet [8 or to the plates 26 and 28 in the air gap therebetween, a U-shaped shield 40 of non-magnetic material is slipped into appropriate grooves in the pole pieces, plates, and block so as to extend along three sides of the permanent magnet and provide in connection with the block to which it is suitably secured a complete enclosing of the magnet.

As can be seen from Fig. 3, the shield coincides with the holding faces of the pole pieces in flush relation thereto and as such does not interfere with the holding qualities thereof.

The air gap A provided between the plates 26 and 28 together with the plates constitutes a shunt circuit for the magnetic holding mechanism and forms a part of the minor flux path designated by the dotted lines B of Fig. 3 and as such provides a holding magnet of great strength whereby through the predetermination of size of the air gap the magnetic fiux in the holding circuit is raised to a maximum. This holding circuit is designated by the dotted lines C of Fig. 3 wherein the holding ends of the mechanism l2 are in contact with the surface of some magnetic material, such as, a part of a machine tool which forms a part of the flux path.

Figs. 6 and '7 are directed to the provision of a magnetic holding mechanism embodying the general principle of the structures of Fig. 1 through 5 and incorporating shunt circuit control means wherein instead of the plates 26 and 28 provided by the structure of Fig. 3 plates 42 and 44 of a the mechanism.

The non-magnetic material 50 is of a predetermined thickness so as to provide a suitable leakage or shunt gap such that upon the movement of the shaft to a position wherein the brass strip is in dotted line position of Fig. 7 the magnetic holding position of the mechanism is at its maximum holding force. With the shaft 48 in full line position of'Fig. '7 the members 52 because of their close physical contacting relation with the plates 42 and 44 a complete shunting of the magnet is effected thus detracting from the holding qualities of the magnetic holding portion of the mechanism and reducing the magnetic strength to a low residual value.

With the provision of the control shaft 48, the mechanism can be readily removed from magnetic holding position merely by a complete shunting of the magnetic flux lines through the manipulation of shaft 48 through Fig. 8 illustrates a modified form of the control shaft of Figs. 6 and 7 wherein a cylindrical shaft 60 of high magnetic permeability material such as mild steel or the like is provided having a pair of arcuate inserts 62 made of non-magnetic material such as brass arranged in the exterior of the shaft oppositely disposed from one another. The inserts 62 in providing leakage or shunt gaps are equally effective as strip 50 of the structure shown by Fig. 7.

Although the shunt circuit gap and control mechanism are shown by the drawings in a specific arrangement relative to the pole pieces and permanent magnet they can be placed anywhere on the pole pieces 28 and 22 and will function equally as well as the structures shown and described hereinabove.

While this invention has been described in connection with certain specific embodiments, the principle involved is susceptible of numerous other applications that will readily occur to persons skilled in the art. The invention, therefore, is limited only as indicated by the scope of the appended claims.

What I claim is:

l. A holding device comprising a permanent magnet, a pair of pole pieces disposed on opposite sides of the magnet terminating at one end in work engaging surfaces spaced apart the thickness of the magnet and at their other ends being disposed toward one another but spaced apart a predetermined distance and a magnetic permeable member closely embraced and rotatable between the ends of the pole pieces disposed toward one another having a flat section of non-permeable material passing through the axis of rotation of the magnetic member incorporated therein such that in one position of the magnetic permeable member the work engaging surfaces of the pole pieces will have maximum holding strength and upon rotation of the member 90, the work engaging surfaces will have minimum holding strength.

2. A holding device comprising a permanent magnet, a pair of relatively flat magnetically permeable members arranged in parallel array on opposite sides of the magnet and a member disposed outwardly of the magnet and rotatably secured between opposed ends of the magnetically permeable members, said member being of magnetic permeability and having a non-magnetic flat element of uniform thickness incorporating centrally therein adapted to provide a leakage gap across the opposed ends of the magnetically permeable members for one position of the rotatable member with the fiat element lying parallel to the magnetically permeable members but which are displaced from leakage gap position L upon rotation of the rotatable member 90 from the aforesaid position thereby providing a flux bridging path across the rotatable member between the opposed ends of the magnetically permeable members.

3. A holding device comprising a permanent magnet, a pair of pole pieces arranged on opposite sides of the magnet each having work engaging surfaces on one end and having their opposite ends in opposed spaced relation, said opposed spaced ends having like concave surfaces, and a cylindrical member fitted between the opposed concave surfaces in close bearing and rotative relation, said cylindrical member comprising a portion of magnetically permeable material and a flat portion of non-magnetic material arranged centrally of the magnetically permeable portion separating the magnetically permeable portion into two like spaced arcuate sections such that in one position of the cylindrical member a leakage gap is provided for maximum holding quality at the work engaging surfaces of the pole pieces and in a second position of the cylindrical member upon rotation of 90 from the first position, the holding quality at the work engaging surfaces of the pole pieces is at a minimum.

4. A holding device comprising a permanent magnet, a pair of pole pieces arranged on opposite sides of the magnet each having work engaging surfaces on one end and having their opposite ends in opposed spaced relation, said opposed spaced ends having like concave surfaces, and a cylindrical member fitted between the opposed concave surfaces in close bearing and rotative relation, said cylindrical member comprising a pair of like arcuate portions of magnetically permeable material spaced apart and separated by a fiat portion of non-magnetic material such that in one position of the cylindrical member a leak age gap is provided for maximum holding quality at the work engaging surfaces of the pole pieces and in a second position of the cylindrical member upon rotation of 90 from the first position, the holding quality at the work engaging surfaces of the pole pieces is at a minimum.

5. A holding device comprising a permanent magnet, a pair of like pole pieces of high magnetic permeability secured to the permanent magnet on opposite sides thereof extending parallel to one another terminating in work engaging surfaces on one end, a pair of like high magnetic permeability members, one secured upon each of the respective pole pieces on the ends thereof oppositely disposed from the work engaging faces thereof, said members extending in a direction toward one another and spaced apart a predetermined distance providing opposed arcuate surfaces, and a cylindrical member mounted for rotation in the space between the arcuate surfaces comprising a pair of semi-cylindrical members of high magnetic permeability having a flat section member of uniform thickness non-magnetic permeability material sandwiched therebetween.

RAYMOND B. ROOF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,778,481 Boucher Oct. 14, 1930 2,179,305 Stickney Nov. 7, 1939 2,268,011 Beechlyn Dec. 30, 1941 2,269,149 Edgar Jan. 6, 1942 2,275,839 Boehne Mar. 10, 1942 2,333,230 Beechlyn Nov. 2, 1943 2,347,023 Beechlyn Apr. 18, 1944 2,442,016 Poole May 25, 1948 FOREIGN PATENTS Number Country Date 444,786 Great Britain Mar. 27, 1936 

